1. Field of the Invention
The present invention relates to an internal combustion engine control apparatus that is equipped with a cylinder deactivation control means for activating or deactivating at least one cylinder of the internal combustion engine.
2. Description of the Background
In order to improve fuel economy performance of internal combustion engines, an internal combustion engine has been conventionally known that is equipped with a cylinder deactivation system. The cylinder deactivation system, in response to operating conditions of the internal combustion engine, deactivates operation of part of a plurality of cylinders by putting the intake valve(s) and the exhaust valve(s) into the inoperative condition (valve lift=0) and operates the other cylinders under a high load condition (large throttle opening), to reduce pumping loss.
In the internal combustion engine equipped with the cylinder deactivation system, since various kinds of controls, such as fuel control, airflow control, and torque control, are performed in response to a determination result whether the valves are in the operative or inoperative conditions, the valve condition need to be determined accurately.
There have been proposed technologies of determining the valve condition such as by utilizing presence or absence of the intake-air pulsation, which synchronize with the intake stroke of each cylinder, detected from output of the airflow sensor (see, for example, Patent Document 1) and by utilizing the air-to-fuel ratio of the exhaust gas (see, for example, Patent Document 2).
Patent Document 1: Japanese Application Laid-open No. 2009-270492
Patent Document 2: Japanese Application Laid-open No. 2012-92745
However, when any one of the intake valve and the exhaust valve malfunctions, such conventional technologies have not been capable of determining the condition of the other valve.